1. Field of the Invention
The invention relates to a method of manufacturing an optical element with a lens-barrel.
2. Description of the Related Art
In recent years, in a method of manufacturing an optical element (or a glass-formed component) in which an optical raw material (or an optical glass raw material) is heat-softened in a heating furnace and thereafter pressed between an upper die and a lower die, there has been used a method in which the optical raw material is held in a frame member set in the inside of a shaping die and is pressed by the upper die and the lower die, and thereby the raw material is caused to flow in the direction of the outer periphery thereof, causing the outer edge of the raw material to tightly join to the inner peripheral surface of the frame member.
There is also known a scheme to improve the adhesion of the optical raw material to the frame member by shaping unevenness in given sites on the inner peripheral surface of the frame member to which the outer edge of an optical element (glass-formed component) is to join. In this manner, a conventional example for improving the adherence of the optical raw material to the frame member is based on an idea of engaging an excess of glass into the depressed portion of the lens-barrel during pressing. This idea is the same in FIG. 5, in which a depression is provided at the lens-barrel position corresponding to a taper-shaped pointed top, and the top is engaged into the depression. In this case, the flow of an excess of glass becomes offset and thus glass does not flow uniformly, thus resulting in adverse effect on the optical performance of the formed lens, such as a bad distribution of refractive index.
In the conventional example described above, the optical element is integrally joined to the frame member, and the frame member is used as a lens-assembling frame (lens frame)